Homeostasis of postmitotic and proliferating cells is maintained by pathways that repress stress. We found that the Caenorhabditis elegans histone 3 lysine 4 (H3K4) demethylases RBR-2 and SPR-5 promoted postmitotic longevity of stress-resistant daf-2 adults, altered pools of methylated H3K4, and promoted silencing of some daf-2 target genes. In addition, RBR-2 and SPR-5 were required for germ cell immortality at a high temperature. Transgenerational proliferative aging was enhanced for spr-5; rbr-2 double mutants, suggesting that these histone demethylases may function sequentially to promote germ cell immortality by targeting distinct H3K4 methyl marks. RBR-2 did not play a comparable role in the maintenance of quiescent germ cells in dauer larvae, implying that it represses stress that occurs as a consequence of germ cell proliferation, rather than stress that accumulates in nondividing cells. We propose that H3K4 demethylase activities promote the maintenance of chromatin states during stressful growth conditions, thereby repressing postmitotic aging of somatic cells as well as proliferative aging of germ cells.
Soybean is one of the most important legumes of the world. Soybean plants are affected by several biotic and abiotic factors as well as insect pests and diseases which lower the quality and production of the crop. In order to overcome these biotic and abiotic challenges, a systematic crop improvement plan has to be followed in order to enhance crop production which involves the use of new technologies and developing new cultivars with desirable qualities. With the completion of the soybean genome sequencing project, it is anticipated that access to desirable gene sequences will advance soybean improvement efforts. Two general approaches for in vitro plant regeneration are used; somatic embryogenesis from immature embryos and organogenesis from mature parts of the plant and seeds. In vitro regeneration in soybean depends upon several physical, biochemical and genetic factors. Different genotypes respond differently to the method of regeneration used. Pyramid soybean is used in several breeding and mapping projects but does not have a regeneration procedure worked out. The goal of our project was to develop an in vitro regeneration procedure for soybean cv. Pyramid that would be amenable to genetic manipulations. We excised cotyledons and embryos from germinating seeds and induced callus with various concentrations of 2,4-D and NAA, used alone or in combination. 2,4-D at 3-21 M concentrations in the culture media produced 100% callus induction from cotyledons. After callus formation we transferred them to BAP and Kinetin containing culture media and obtained roots and shoots; 5 M BAP was the most effective for that purpose. Fully developed plants were transplanted to the pots in less than three months where they produced healthy seeds in July.
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